.demo-button 
  .rv-button {
    margin: 0 8px 12px 0;
  }

 .demo-button  .rv-button-group .rv-button{
     
      margin: 0;
    
  }

.rv-button {
    width: 40vw;
    text-align: center;
}
.btnw{
    width: 100vw;
    height: 10vh;
    display: flex;
    align-items: center;
    justify-content: center;
}